Similar to the other projects in this application for a Mycology Research Unit, Project I will focus on Cryptococcus neoformans and efforts to identify and verify potential targets leads to advances in the diagnosis, treatment or prevention of cryptococcosis. The natural reservoir of C. neoformans is exogenous, and cryptococcosis is acquired by inhalation of the yeast cells or basidiospores. Both environmental and clinical isolates of C. neoformans vary extensively in the expression of many phenotypes including properties known to affect the clinical outcome. Project I will investigate the association of phenotype and genotype in C. neoformans. Isolates will be obtained globally from a variety of sources, and populations associated with pathogenicity will be characterized genetically. The distribution and relatedness of strains will be analyzed at the DNA sequence level. Thus, the populations structure of C. neoformans will be investigated using defined genotypic markers. With analysis of quantitative trait, loci, specific genotypes will be identified that represent clones that have significantly diverged with respect to clinically relevant phenotypes, including susceptibility to antifungal drugs and the expression of virulence factors. Two broad specific aims are proposed: The first will involved an experiment approach to construct a genetic linkage map of C. neoformans. The genetic traits to be mapped will include those relating to signal transduction (Project II), antifungal drug targets (Project III), and temperature-regulated growth (Project IV). The second aim will investigate genomic evolution and phenotypic variation in natural populations of C. neoformans. Both approaches will serve to correlate genotypes with clinically relevant phenotypes.